1. Field of the Invention
The present invention relates to a projection apparatus. More particularly, the present invention relates to a structure of a scanning projection apparatus.
2. Description of Related Art
Referring to FIG. 1, a conventional scanning projection apparatus 100 includes an actuator 110, a light source 120, a projection lens 130, a collimating lens 140, and a reflector 150. The light source 120 emits different light beams 122 sequentially according to image data to be displayed. The reflector 150 is disposed on the actuator 110, and the actuator 110 is suitable for driving the reflector 150 so as to reflect the light beams 122 emitted by the light source 120 sequentially along different transmission paths. The projection lens 130 and the collimating lens 140 are disposed on the transmission paths of the light beams 122 after being reflected by the reflector 150. The collimating lens 140 is located between the actuator 110 and the projection lens 130. The light beams 122 reflected by the reflector 150 at different time are projected to different positions on the screen 200 through different paths by the projection lens 130, so as to form an image 210. In other words, the reflector 150 on the actuator 110 faces different directions at different time so that the light beams 122 are reflected by the reflector 150 along different transmission paths and projected to different positions on the screen 200 by the projection lens 130 so as to form an image 210.
For example, when the resolution of the image 210 projected by the scanning projection apparatus 100 is M×N and the refresh frequency of the image 210 is 60 Hz, the light source 120 has to sequentially emit (M×N) light beams 122 within 1/60 s, and the reflector 150 on the actuator 110 has to swing at least (½×N) times within 1/60 s. The reflector 150 on the actuator 110 faces different directions that the direction changes caused by the swing at different time within a frame time (i.e. 1/60 s), thus, the (M×N) light beams 122 emitted by the light source 120 can be sequentially projected to the 1st column 1st row, the 1st column 2nd row, . . . , the Nth column (M−1)th row, and the Nth column Mth row of the image 210.
The swing frequency of the actuator 110 increases accordingly when the resolution (M×N) of the image 210 projected by the scanning projection apparatus 100 is higher. Thus, the size of the image 210 projected by the scanning projection apparatus 100 is limited considerably by the operation frequency of the actuator 110. Besides, in the conventional scanning projection apparatus 100, no device except optics elements which assist in the light beams 122 in transmission, is placed in the space between the actuator 110 (or the reflector 150) and the reflection light source 120 to avoid an effect on the transmission of the light beams 122. Accordingly, the volume of the conventional scanning projection apparatus 100 cannot be further reduced due to the space between the actuator 110 and the light source 120, and it causes problems in a layout of elements in the conventional scanning projection apparatus 100. Moreover, stray lights may be produced when the reflector 150 is reflecting the light beams 122, so that the quality of the image projected by the scanning projection apparatus 100 may be affected.